I. Field of the Invention
The present invention relates to the control of infinitely variable transmissions with electric variator.
More precisely, its subject is a method of damping the oscillating modes of an infinitely variable transmission with electric variator, comprising a heat engine and at least two electric machines, as well as a supervising device, affording regulation of the torque at the wheels and of the status of the heat engine.
This invention applies to a vehicle equipped with a heat engine and with an infinitely variable transmission with electric variator, which exhibits the particular feature of not comprising any coupler, clutch or converter, between the heat engine and the transmission.
It finds a favored, but nonlimiting application on a transmission device of the type comprising at least two parallel paths for power transmission, one path containing a kinematic chain with fixed gearing, and another path containing a continuous speed variator, composed of two electric machines.
II. Description of Related Art
The publication FR 2 823 281 discloses a device of the type indicated above, according to which the various paths are connected on the one hand to an input mechanical distributor linked to a mechanical energy source such as a heat engine, and on the other hand to an output mechanical distributor linked to the wheels of the vehicle. The input and output mechanical distributors, are preferably, but not necessarily, epicyclic gear trains.
The transmission described in this publication thus comprises two electric machines linked by an energy buffer element, which are integrated into a kinematic chain having four input and output shafts, respectively connected to the heat engine, to the wheels, and to the electric motors.
According to a customary arrangement within the field, a transmission calculation unit establishes instruction setpoints for each actuator (the two electric machines, and possibly the heat engine), making it possible to place the transmission on an operating point determined by other calculation modules called “higher monitoring layers”, in the following four basic situations:                “torque tracking”, where the driver presses the accelerator: the target of the computer is a wheel torque and a status of the heat engine required by the monitor (this is the commonest case where the heat engine provides an engine torque),        “fuel cutoff”, where the driver does not press the accelerator, and where injection is cut off to the heat engine and the latter provides a resistive torque; the target is a thermal status required by the monitor,        “speed creeping”, where the vehicle moves at low speed, the driver pressing neither the accelerator nor the brake; the target is a thermal status required by the monitor, and        “torque creeping”, where the vehicle moves at low speed, the driver pressing the brake pedal.        
The calculation unit in charge of establishing the instruction setpoints of each actuator must in particular comply with the performance specifications, and must resist various disturbances, or “control noise” of the system, whilst affording regulation of the energy buffer element.
Among these disturbances are the oscillations caused by all the stiffnesses lying between the engine and the wheels. The better the performances, the more sensitive to these stiffnesses are the compliance and robustness of the regulating of the engine power plant.
Ignoring them restricts the performance of the regulating device, since excessive performance degrades the robustness, brings about oscillations, and leads to the instability of the regulating device.